[libc-commits] [libc] [libc] Add `FILENO` related macros to `unistd.h`. (PR #124688)

[Nick Desaulniers via libc-commits]

https://github.com/nickdesaulniers approved this pull request.

Thanks for the patch.

A better source to cite rather than the man page is POSIX itself, which mandates these symbolic constants have these specific values.

https://pubs.opengroup.org/onlinepubs/9799919799/basedefs/unistd.h.html

https://github.com/llvm/llvm-project/pull/124688